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PHP CodeIgniter Basics

Introduction​

CodeIgniter is a lightweight, open-source PHP framework that follows the Model-View-Controller (MVC) architectural pattern. Created by EllisLab and now maintained by the British Columbia Institute of Technology, CodeIgniter is designed to help developers build web applications faster by providing a rich set of libraries for common tasks while requiring minimal configuration.

In this tutorial, we'll explore the basics of CodeIgniter 4 (the latest major version), understand its core concepts, and build simple applications to demonstrate its capabilities. Whether you're new to PHP frameworks or looking to expand your toolkit, CodeIgniter offers a gentle learning curve with powerful features.

Why Choose CodeIgniter?​

Before diving into the code, let's understand why CodeIgniter might be the right framework for your projects:

  • Small Footprint: CodeIgniter is lightweight and has minimal server requirements
  • Great Performance: It's known for being faster than many other PHP frameworks
  • Simple Configuration: Minimal setup required to get started
  • Documentation: Comprehensive and well-maintained documentation
  • Community Support: Active community and regular updates
  • Low Learning Curve: Easy to learn, especially if you're familiar with PHP

Setting Up CodeIgniter​

Installation​

There are several ways to install CodeIgniter 4. We'll cover the two most common methods:

Method 1: Using Composer​

bash
# Create a project using Composer
composer create-project codeigniter4/appstarter project-name

# Navigate to your project
cd project-name

# Start the development server
php spark serve

Method 2: Manual Download​

  1. Download the latest version from CodeIgniter's official website
  2. Extract the files to your web server directory
  3. Configure your web server to point to the public folder

Understanding the Project Structure​

After installation, you'll see a directory structure like this:

project-root/
├── app/                    # Your application code goes here
│   ├── Config/             # Configuration files
│   ├── Controllers/        # Controllers
│   ├── Models/             # Models
│   ├── Views/              # Views
│   └── ...
├── public/                 # Publicly accessible files
│   ├── index.php           # Entry point to the application
│   ├── assets/             # CSS, JavaScript, images, etc.
│   └── ...
├── system/                 # CodeIgniter core files (don't modify)
├── writable/               # Logs, cache, and other writable files
├── tests/                  # Unit tests
└── spark                   # Command-line tool

MVC Architecture in CodeIgniter​

CodeIgniter follows the Model-View-Controller pattern, which separates your application into three main components:

  • Model: Manages data and business logic
  • View: Handles the presentation layer (HTML output)
  • Controller: Coordinates between Model and View, processes requests

Let's see how each component works in CodeIgniter.

Controllers: The Entry Point​

Controllers handle user requests and coordinate the application's response. They are the central point of your application's logic.

Creating Your First Controller​

Create a file named Hello.php in the app/Controllers directory:

php
<?php

namespace App\Controllers;

use CodeIgniter\Controller;

class Hello extends Controller
{
    public function index()
    {
        return "Hello, CodeIgniter!";
    }
    
    public function greet($name = 'World')
    {
        return "Hello, {$name}!";
    }
}

Accessing Controllers​

With the controller above, you can access:

  • http://localhost:8080/hello - Shows "Hello, CodeIgniter!"
  • http://localhost:8080/hello/greet/John - Shows "Hello, John!"

Loading Views from Controllers​

Let's modify our controller to use a view:

php
<?php

namespace App\Controllers;

use CodeIgniter\Controller;

class Hello extends Controller
{
    public function index()
    {
        $data = [
            'title' => 'Welcome to CodeIgniter',
            'message' => 'Hello, CodeIgniter!'
        ];
        
        return view('hello_view', $data);
    }
}

Views: The Presentation Layer​

Views contain the HTML and presentation code. They receive data from controllers and display it to users.

Creating Your First View​

Create a file named hello_view.php in the app/Views directory:

php
<!DOCTYPE html>
<html>
<head>
    <title><?= $title ?></title>
</head>
<body>
    <h1><?= $title ?></h1>
    <p><?= $message ?></p>
    
    <p>Current time: <?= date('Y-m-d H:i:s') ?></p>
</body>
</html>

Using View Layouts​

CodeIgniter 4 supports view layouts to avoid code duplication. Let's create a layout:

  1. Create app/Views/layouts/main.php:
php
<!DOCTYPE html>
<html>
<head>
    <title><?= $title ?? 'CodeIgniter 4' ?></title>
    <link rel="stylesheet" href="/assets/css/style.css">
</head>
<body>
    <header>
        <h1>My CodeIgniter Application</h1>
        <nav>
            <ul>
                <li><a href="/">Home</a></li>
                <li><a href="/about">About</a></li>
                <li><a href="/contact">Contact</a></li>
            </ul>
        </nav>
    </header>
    
    <main>
        <?= $this->renderSection('content') ?>
    </main>
    
    <footer>
        <p>&copy; <?= date('Y') ?> My Application</p>
    </footer>
    
    <script src="/assets/js/script.js"></script>
</body>
</html>
  1. Create a view that uses the layout:
php
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2><?= $title ?></h2>
    <p><?= $message ?></p>
<?= $this->endSection() ?>

Models: Working with Data​

Models handle data access and business logic. They connect to databases and provide methods to manipulate data.

Creating Your First Model​

Create a file named UserModel.php in the app/Models directory:

php
<?php

namespace App\Models;

use CodeIgniter\Model;

class UserModel extends Model
{
    protected $table = 'users';
    protected $primaryKey = 'id';
    
    protected $allowedFields = ['name', 'email', 'password'];
    
    protected $useTimestamps = true;
    protected $createdField = 'created_at';
    protected $updatedField = 'updated_at';
    
    protected $beforeInsert = ['hashPassword'];
    
    protected function hashPassword(array $data)
    {
        if (isset($data['data']['password'])) {
            $data['data']['password'] = password_hash($data['data']['password'], PASSWORD_DEFAULT);
        }
        
        return $data;
    }
}

Using Models in Controllers​

Now let's use our model in a controller:

php
<?php

namespace App\Controllers;

use App\Models\UserModel;
use CodeIgniter\Controller;

class Users extends Controller
{
    public function index()
    {
        $userModel = new UserModel();
        $data['users'] = $userModel->findAll();
        
        return view('users/index', $data);
    }
    
    public function create()
    {
        return view('users/create');
    }
    
    public function store()
    {
        $userModel = new UserModel();
        
        $data = [
            'name' => $this->request->getPost('name'),
            'email' => $this->request->getPost('email'),
            'password' => $this->request->getPost('password')
        ];
        
        $userModel->insert($data);
        
        return redirect()->to('/users');
    }
}

Working with Database​

Database Configuration​

Configure your database in app/Config/Database.php:

php
public $default = [
    'DSN'      => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => 'password',
    'database' => 'codeigniter',
    'DBDriver' => 'MySQLi',
    'DBPrefix' => '',
    'pConnect' => false,
    'DBDebug'  => (ENVIRONMENT !== 'production'),
    'charset'  => 'utf8',
    'DBCollat' => 'utf8_general_ci',
    'swapPre'  => '',
    'encrypt'  => false,
    'compress' => false,
    'strictOn' => false,
    'failover' => [],
    'port'     => 3306,
];

Using the Query Builder​

CodeIgniter provides a Query Builder class for working with databases:

php
<?php

namespace App\Controllers;

use CodeIgniter\Controller;

class Posts extends Controller
{
    public function index()
    {
        $db = \Config\Database::connect();
        $builder = $db->table('posts');
        
        $query = $builder->select('posts.*, users.name as author')
                         ->join('users', 'users.id = posts.user_id')
                         ->where('posts.status', 'published')
                         ->orderBy('posts.created_at', 'DESC')
                         ->get();
        
        $data['posts'] = $query->getResult();
        
        return view('posts/index', $data);
    }
}

Forms and Validation​

Creating a Form​

Let's create a simple registration form:

php
<!-- app/Views/register.php -->
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2>Register</h2>
    
    <?php if (session()->has('errors')): ?>
        <div class="errors">
            <ul>
                <?php foreach (session('errors') as $error): ?>
                    <li><?= $error ?></li>
                <?php endforeach ?>
            </ul>
        </div>
    <?php endif ?>
    
    <form action="/register" method="post">
        <?= csrf_field() ?>
        
        <div>
            <label for="name">Name</label>
            <input type="text" name="name" id="name" value="<?= old('name') ?>">
        </div>
        
        <div>
            <label for="email">Email</label>
            <input type="email" name="email" id="email" value="<?= old('email') ?>">
        </div>
        
        <div>
            <label for="password">Password</label>
            <input type="password" name="password" id="password">
        </div>
        
        <div>
            <label for="password_confirm">Confirm Password</label>
            <input type="password" name="password_confirm" id="password_confirm">
        </div>
        
        <div>
            <button type="submit">Register</button>
        </div>
    </form>
<?= $this->endSection() ?>

Implementing Form Validation​

Let's add validation to our registration form:

php
<?php

namespace App\Controllers;

use App\Models\UserModel;
use CodeIgniter\Controller;

class Auth extends Controller
{
    public function register()
    {
        return view('register');
    }
    
    public function processRegistration()
    {
        // Validation rules
        $rules = [
            'name' => 'required|min_length[3]|max_length[50]',
            'email' => 'required|valid_email|is_unique[users.email]',
            'password' => 'required|min_length[8]',
            'password_confirm' => 'required|matches[password]'
        ];
        
        // Custom error messages
        $messages = [
            'name' => [
                'required' => 'Name is required',
                'min_length' => 'Name must be at least 3 characters long'
            ],
            'email' => [
                'is_unique' => 'This email is already registered'
            ]
        ];
        
        // Run validation
        if (! $this->validate($rules, $messages)) {
            return redirect()->back()->withInput()->with('errors', $this->validator->getErrors());
        }
        
        // If validation passes, store the user
        $userModel = new UserModel();
        
        $userModel->insert([
            'name' => $this->request->getPost('name'),
            'email' => $this->request->getPost('email'),
            'password' => $this->request->getPost('password')
        ]);
        
        return redirect()->to('/login')->with('message', 'Registration successful! You can now log in.');
    }
}

Routing in CodeIgniter​

Routes define which controller and method should handle a specific URL request.

Basic Routes​

Edit app/Config/Routes.php to define your routes:

php
// Default route
$routes->get('/', 'Home::index');

// Simple route
$routes->get('about', 'Pages::about');

// Route with parameters
$routes->get('users/(:num)', 'Users::show/$1');

// POST route
$routes->post('register', 'Auth::processRegistration');

// Route group with prefix
$routes->group('admin', function($routes) {
    $routes->get('dashboard', 'Admin::dashboard');
    $routes->get('users', 'Admin::users');
    $routes->get('settings', 'Admin::settings');
});

// Resource routes (RESTful)
$routes->resource('api/products');

Working with Sessions​

CodeIgniter provides a powerful session library for managing user sessions.

Session Configuration​

Configure sessions in app/Config/App.php:

php
public $sessionDriver = 'CodeIgniter\Session\Handlers\FileHandler';
public $sessionCookieName = 'ci_session';
public $sessionExpiration = 7200;
public $sessionSavePath = WRITEPATH . 'session';
public $sessionMatchIP = false;
public $sessionTimeToUpdate = 300;
public $sessionRegenerateDestroy = false;

Using Sessions​

php
<?php

namespace App\Controllers;

use CodeIgniter\Controller;

class Auth extends Controller
{
    public function login()
    {
        return view('login');
    }
    
    public function processLogin()
    {
        $email = $this->request->getPost('email');
        $password = $this->request->getPost('password');
        
        // Validate credentials (simplified for example)
        $userModel = new \App\Models\UserModel();
        $user = $userModel->where('email', $email)->first();
        
        if ($user && password_verify($password, $user['password'])) {
            // Set session data
            $session = session();
            $session->set([
                'user_id' => $user['id'],
                'user_name' => $user['name'],
                'user_email' => $user['email'],
                'logged_in' => true
            ]);
            
            return redirect()->to('/dashboard');
        }
        
        return redirect()->back()->with('error', 'Invalid credentials');
    }
    
    public function logout()
    {
        // Clear session data
        session()->destroy();
        
        return redirect()->to('/login');
    }
    
    public function dashboard()
    {
        // Check if user is logged in
        if (!session()->get('logged_in')) {
            return redirect()->to('/login');
        }
        
        $data['user_name'] = session()->get('user_name');
        
        return view('dashboard', $data);
    }
}

File Uploads​

CodeIgniter makes file uploads easy with its built-in file upload class.

Creating a File Upload Form​

php
<!-- app/Views/upload_form.php -->
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2>Upload File</h2>
    
    <?php if (session()->has('error')): ?>
        <div class="error"><?= session('error') ?></div>
    <?php endif ?>
    
    <?php if (session()->has('success')): ?>
        <div class="success"><?= session('success') ?></div>
    <?php endif ?>
    
    <form action="/upload" method="post" enctype="multipart/form-data">
        <?= csrf_field() ?>
        
        <div>
            <label for="file">Select File</label>
            <input type="file" name="userfile" id="file">
        </div>
        
        <div>
            <button type="submit">Upload</button>
        </div>
    </form>
<?= $this->endSection() ?>

Handling File Uploads​

php
<?php

namespace App\Controllers;

use CodeIgniter\Controller;

class Upload extends Controller
{
    public function index()
    {
        return view('upload_form');
    }
    
    public function process()
    {
        $validationRule = [
            'userfile' => [
                'label' => 'Image File',
                'rules' => 'uploaded[userfile]'
                    . '|is_image[userfile]'
                    . '|mime_in[userfile,image/jpg,image/jpeg,image/png]'
                    . '|max_size[userfile,2048]',
            ],
        ];
        
        if (!$this->validate($validationRule)) {
            return redirect()->back()->with('error', $this->validator->getError('userfile'));
        }
        
        $file = $this->request->getFile('userfile');
        
        if ($file->isValid() && !$file->hasMoved()) {
            $newName = $file->getRandomName();
            $file->move(WRITEPATH . 'uploads', $newName);
            
            return redirect()->back()->with('success', 'File uploaded successfully: ' . $file->getClientName());
        }
        
        return redirect()->back()->with('error', 'Failed to upload file.');
    }
}

Filters (Middleware)​

Filters in CodeIgniter are similar to middleware in other frameworks. They can run before or after controller execution.

Creating a Filter​

Create a file named AuthFilter.php in the app/Filters directory:

php
<?php

namespace App\Filters;

use CodeIgniter\Filters\FilterInterface;
use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;

class AuthFilter implements FilterInterface
{
    public function before(RequestInterface $request, $arguments = null)
    {
        // Check if user is logged in
        if (!session()->get('logged_in')) {
            return redirect()->to('/login');
        }
    }
    
    public function after(RequestInterface $request, ResponseInterface $response, $arguments = null)
    {
        // Do something after the controller executes
    }
}

Registering and Using Filters​

Configure filters in app/Config/Filters.php:

php
public $aliases = [
    'csrf'     => \CodeIgniter\Filters\CSRF::class,
    'toolbar'  => \CodeIgniter\Filters\DebugToolbar::class,
    'honeypot' => \CodeIgniter\Filters\Honeypot::class,
    'auth'     => \App\Filters\AuthFilter::class,
];

// Always enabled filters
public $globals = [
    'before' => [
        'csrf',
    ],
    'after' => [
        'toolbar',
    ],
];

// Filters for specific routes
public $methods = [];

// Filter for specific routes
public $filters = [
    'auth' => ['before' => ['dashboard', 'admin/*']],
];

Practical Project: Todo List Application​

Let's put everything together by building a simple todo list application.

Step 1: Create the Database Table​

sql
CREATE TABLE todos (
    id INT(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    description TEXT,
    status ENUM('pending', 'completed') DEFAULT 'pending',
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

Step 2: Create the Model​

php
<?php

namespace App\Models;

use CodeIgniter\Model;

class TodoModel extends Model
{
    protected $table = 'todos';
    protected $primaryKey = 'id';
    
    protected $allowedFields = ['title', 'description', 'status'];
    
    protected $useTimestamps = true;
    protected $createdField = 'created_at';
    protected $updatedField = 'updated_at';
    
    public function getPendingTodos()
    {
        return $this->where('status', 'pending')->findAll();
    }
    
    public function getCompletedTodos()
    {
        return $this->where('status', 'completed')->findAll();
    }
}

Step 3: Create the Controller​

php
<?php

namespace App\Controllers;

use App\Models\TodoModel;
use CodeIgniter\Controller;

class Todos extends Controller
{
    protected $todoModel;
    
    public function __construct()
    {
        $this->todoModel = new TodoModel();
    }
    
    public function index()
    {
        $data = [
            'title' => 'Todo List',
            'pendingTodos' => $this->todoModel->getPendingTodos(),
            'completedTodos' => $this->todoModel->getCompletedTodos()
        ];
        
        return view('todos/index', $data);
    }
    
    public function create()
    {
        return view('todos/create', ['title' => 'Create Todo']);
    }
    
    public function store()
    {
        $rules = [
            'title' => 'required|min_length[3]|max_length[255]'
        ];
        
        if (!$this->validate($rules)) {
            return redirect()->back()->withInput()->with('errors', $this->validator->getErrors());
        }
        
        $this->todoModel->insert([
            'title' => $this->request->getPost('title'),
            'description' => $this->request->getPost('description')
        ]);
        
        return redirect()->to('/todos')->with('message', 'Todo created successfully!');
    }
    
    public function edit($id)
    {
        $data = [
            'title' => 'Edit Todo',
            'todo' => $this->todoModel->find($id)
        ];
        
        if (empty($data['todo'])) {
            return redirect()->to('/todos')->with('error', 'Todo not found');
        }
        
        return view('todos/edit', $data);
    }
    
    public function update($id)
    {
        $rules = [
            'title' => 'required|min_length[3]|max_length[255]'
        ];
        
        if (!$this->validate($rules)) {
            return redirect()->back()->withInput()->with('errors', $this->validator->getErrors());
        }
        
        $this->todoModel->update($id, [
            'title' => $this->request->getPost('title'),
            'description' => $this->request->getPost('description'),
            'status' => $this->request->getPost('status')
        ]);
        
        return redirect()->to('/todos')->with('message', 'Todo updated successfully!');
    }
    
    public function delete($id)
    {
        $this->todoModel->delete($id);
        
        return redirect()->to('/todos')->with('message', 'Todo deleted successfully!');
    }
    
    public function complete($id)
    {
        $this->todoModel->update($id, ['status' => 'completed']);
        
        return redirect()->to('/todos')->with('message', 'Todo marked as completed!');
    }
}

Step 4: Create the Views​

app/Views/todos/index.php:

php
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2>Todo List</h2>
    
    <?php if (session()->has('message')): ?>
        <div class="alert alert-success"><?= session('message') ?></div>
    <?php endif ?>
    
    <?php if (session()->has('error')): ?>
        <div class="alert alert-danger"><?= session('error') ?></div>
    <?php endif ?>
    
    <div class="actions">
        <a href="/todos/create" class="btn btn-primary">Create New Todo</a>
    </div>
    
    <h3>Pending Todos</h3>
    
    <?php if (empty($pendingTodos)): ?>
        <p>No pending todos.</p>
    <?php else: ?>
        <table class="table">
            <thead>
                <tr>
                    <th>Title</th>
                    <th>Description</th>
                    <th>Created</th>
                    <th>Actions</th>
                </tr>
            </thead>
            <tbody>
                <?php foreach ($pendingTodos as $todo): ?>
                    <tr>
                        <td><?= $todo['title'] ?></td>
                        <td><?= $todo['description'] ?></td>
                        <td><?= date('Y-m-d', strtotime($todo['created_at'])) ?></td>
                        <td>
                            <a href="/todos/edit/<?= $todo['id'] ?>" class="btn btn-sm btn-primary">Edit</a>
                            <a href="/todos/complete/<?= $todo['id'] ?>" class="btn btn-sm btn-success">Complete</a>
                            <a href="/todos/delete/<?= $todo['id'] ?>" class="btn btn-sm btn-danger" onclick="return confirm('Are you sure?')">Delete</a>
                        </td>
                    </tr>
                <?php endforeach ?>
            </tbody>
        </table>
    <?php endif ?>
    
    <h3>Completed Todos</h3>
    
    <?php if (empty($completedTodos)): ?>
        <p>No completed todos.</p>
    <?php else: ?>
        <table class="table">
            <thead>
                <tr>
                    <th>Title</th>
                    <th>Description</th>
                    <th>Completed</th>
                    <th>Actions</th>
                </tr>
            </thead>
            <tbody>
                <?php foreach ($completedTodos as $todo): ?>
                    <tr>
                        <td><s><?= $todo['title'] ?></s></td>
                        <td><?= $todo['description'] ?></td>
                        <td><?= date('Y-m-d', strtotime($todo['updated_at'])) ?></td>
                        <td>
                            <a href="/todos/delete/<?= $todo['id'] ?>" class="btn btn-sm btn-danger" onclick="return confirm('Are you sure?')">Delete</a>
                        </td>
                    </tr>
                <?php endforeach ?>
            </tbody>
        </table>
    <?php endif ?>
<?= $this->endSection() ?>

app/Views/todos/create.php:

php
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2>Create Todo</h2>
    
    <?php if (session()->has('errors')): ?>
        <div class="alert alert-danger">
            <ul>
                <?php foreach (session('errors') as $error): ?>
                    <li><?= $error ?></li>
                <?php endforeach ?>
            </ul>
        </div>
    <?php endif ?>
    
    <form action="/todos/store" method="post">
        <?= csrf_field() ?>
        
        <div class="form-group">
            <label for="title">Title</label>
            <input type="text" name="title" id="title" class="form-control" value="<?= old('title') ?>">
        </div>
        
        <div class="form-group">
            <label for="description">Description</label>
            <textarea name="description" id="description" class="form-control" rows="5"><?= old('description') ?></textarea>
        </div>
        
        <div class="form-group">
            <button type="submit" class="btn btn-primary">Create Todo</button>
            <a href="/todos" class="btn btn-secondary">Cancel</a>
        </div>
    </form>
<?= $this->endSection() ?>

app/Views/todos/edit.php:

php
<?= $this->extend('layouts/main') ?>

<?= $this->section('content') ?>
    <h2>Edit Todo</h2>
    
    <?php if (session()->has('errors')): ?>
        <div class="alert alert-danger">
            <ul>
                <?php foreach (session('errors') as $error): ?>
                    <li><?= $error ?></li>
                <?php endforeach ?>
            </ul>
        </div>
    <?php endif ?>
    
    <form action="/todos/update/<?= $todo['id'] ?>" method="post">
        <?= csrf_field() ?>
        
        <div class="form-group">
            <label for="title">Title</label>
            <input type="text" name="title" id="title" class="form-control" value="<?= old('title', $todo['title']) ?>">
        </div>
        
        <div class="form-group">
            <label for="description">Description</label>
            <textarea name="description" id="description" class="form-control" rows="5"><?= old('description', $todo['description']) ?></textarea>
        </div>
        
        <div class="form-group">
            <label for="status">Status</label>
            <select name="status" id="status" class="form-control">
                <option value="pending" <?= $todo['status'] == 'pending' ? 'selected' : '' ?>>Pending</option>
                <option value="completed" <?= $todo['status'] == 'completed' ? 'selected' : '' ?>>Completed</option>
            </select>
        </div>
        
        <div class="form-group">
            <button type="submit" class="btn btn-primary">Update Todo</button>
            <a href="/todos" class="btn btn-secondary">Cancel</a>
        </div>
    </form>
<?= $this->endSection() ?>

Step 5: Set Up Routes​

php
// app/Config/Routes.php
$routes->get('todos', 'Todos::index');
$routes->get('todos/create', 'Todos::create');
$routes->post('todos/store', 'Todos::store');
$routes->get('todos/edit/(:num)', 'Todos::edit/$1');
$routes->post('todos/update/(:num)', 'Todos::update/$1');
$routes->get('todos/delete/(:num)', 'Todos::delete/$1');
$routes->get('todos/complete/(:num)', 'Todos::complete/$1');

Best Practices for CodeIgniter Development​

  1. Follow MVC Pattern: Keep your code organize

If you spot any mistakes on this website, please let me know at [email protected]. I’d greatly appreciate your feedback! :)